JPS6231720A - Damper device of magnetic bearing - Google Patents

Abstract

PURPOSE:To prevent resonance phenomenon by adjusting size of a clearance in the radial direction made by a stationary shaft and a rotating body and absorbing vibration of bearing members caused by resonance phenomenon. CONSTITUTION:Resonance phenomenon occurs by mutual repulsion force between magnets 30, 32 and mass of a rotating body 21, and vibration is going to be larger more and more. But when the rotational speed of the rotating body is increased and entire absorption of resonance energy becomes impossible, fluid existing outside the rotating body 21 goes into and comes out of the second clearance 26 formed by the rotating body 21 and a stationary shaft 23 through a through hole 28. Then, damper effect is given and vibration energy is absorbed, and vibration of related members due to resonance phenomenon can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a magnetic bearing chip chisel device. More specifically, it relates to a magnetically levitated hydrodynamic bearing chip chisel device equipped with a polygon mirror as an optical deflector.

(Prior Art) In conventionally used magnetically levitated hydrodynamic bearings, a damper device is employed to prevent natural vibrations in the thrust direction that occur during rotation of the hydrodynamic bearing. The entire configuration will be explained below based on FIG. 4 of the attached drawings. FIG. 5 shows a typical example of a magnetically levitated fluid bearing conventionally employed in a rotating polygon mirror of an optical deflector.

Housing a has an upper frame 1, a lower frame 2, and a side frame 3.
A rotating body consisting of a shaft 5 fixed to the lower frame 2 inside thereof, a cylindrical rotating shaft 6 rotatably fitted on the outer periphery of this shaft, and related members attached to the rotating shaft 6. Collect RTh. The related members of the rotating shaft include a polygon mirror 8 mounted on the outer periphery of the rotating shaft supported by a flange 7, a magnet 9 provided on the outer periphery of the rotating shaft below the flange 7, and a thrust bearing mounted on the lower end of this magnet. 10 and a permanent magnet 11 fixed to the lower thrust receiving side. There is an appropriate gap cf between this rotating body ratio and the fixed shaft 5.
Hold. Further, on the outer periphery of the rotating shaft 6, a groove for generating dynamic pressure, for example, a Herring groove hl is formed. A stator 12 made of a coil is provided on the side of the side frame 3 facing the magnet 9. Reference numeral 13 denotes a support plate for a Hall element 14, which detects and controls the rotational speed of the rotating body R.

One permanent magnet 15 is provided on the lower frame 2 so as to face the permanent magnet 11 attached to the lower end of the thrust receiver 10 so as to be movable up and down by the entire dump mechanism 16. The permanent magnets 11 and 15 have the same polarity. Further, the damper device 16 described above is entirely housed in the lower frame below the permanent magnet 15. For example, this Danchisel device is an elastic member! Ill be.

First, when the coil of the stator 12 is excited, the stator coil and the magnet 9 provided on the rotating shaft 6 cooperate to rotate the rotating shaft 6 together with the polygon mirror 8 in a predetermined direction. In response to this rotation, fluid supplied from a fluid inlet (not shown) passes through the gap cf and flows into the Hering-Zehne groove, generating dynamic pressure to maintain the rotating shaft 6 in the radial direction. At the same time as the rotating shaft 6 is rotated in a predetermined direction, the repulsive action between the magnet 15 provided at the lower end of the thrust receiver 10 and the magnet 15 provided on the lower frame 2 causes the rotating shaft 6 to float in the thrust direction, and the upper surface of the fixed shaft 5 rotates. The gap d formed inside the body box is maintained at an appropriate interval, and the rotating body R is configured to rotate smoothly.

However, there is a risk that natural vibrations may occur in the thrust direction during rotation, so in order to absorb these vibrations, a hammer chisel device 16 as shown in FIG. 4 is provided on the lower frame. The damp chisel device is made of an elastic body, and achieves a damping effect by adjusting the fluid pressure by moving the magnet 15 up and down in accordance with the fluid pressure in the thrust direction.

(Problems to be Solved by the Invention) The Dantsuk device of the above-mentioned conventional example is provided in contact with magnets that emit reciprocal waves, and has a structure that directly absorbs the natural vibrations of both magnets in the thrust direction, so its structure is complicated and Problems such as having to become dog-shaped were obvious.

(Means and effects for solving all the problems) In the present invention, in order to absorb the natural vibration during the rotation of the rotating body equipped with a rotating polygon mirror and the fixed shaft, In order to absorb natural vibrations by adjusting the size of the gap in the radial direction or by adjusting the fluid pressure formed by the rotational levitation of the rotating body, fluid is supplied from the outside into the gap between the rotating body and the fixed shaft. It provides a configuration in which the supplied holes are fully drilled, and the holes are drilled in the rotating body or the fixed shaft.

When a rotating body is supported by a fixed shaft and rotates, when the ratio of the rotational speed to the natural vibration determined by the repulsive force of a pair of magnets with opposite polarities and the mass of the rotating body becomes an integral multiple, a resonance phenomenon occurs. is caused, and when this vibration gradually increases, the radial gap formed between the rotating body and the fixed shaft is configured to absorb the resonance energy, or the radial gap is capable of absorbing this energy. When it runs out, fluid supplied from the outside through the hole enters and exits the gap formed between the rotating body and the fixed shaft, resulting in the so-called Dunnomi effect, which absorbs vibrational energy due to resonance. , it is possible to prevent the occurrence of a resonance phenomenon due to related members.

(Example) Examples of the present invention will be described below with reference to the accompanying drawings. Attached Drawings FIGS. 1, 2, 3, and 4 are route diagrams illustrating different embodiments, and each shows a fixed shaft and a rotating body with the housing and other attached members omitted.

Reference numeral 21 is a rotary body with attached members omitted, and the lower frame 2
It is rotatably inserted into a fixed shaft 23 fixed to 2. A first gap 24 exists in the radial direction between the inner surface of the rotating body 21 and the outer periphery of the fixed shaft 23, and a second gap 26 is entirely formed between the upper surface of the fixed shaft 23 and the inner surface of the rotating body 21. The rotary shaft 21 is provided with a hole 28 that communicates with the second cavity 26 from the outside. A magnet 30 is provided at the lower end of the rotating body 21, and another magnet 32 is provided on the upper surface of the lower frame 22 so as to face the magnet 30. The magnets 30, 32 are magnetized to form the same rif.

The rotating body 21 rotates, and the fluid flows into the first gap 24 and the second gap 2.
6, and due to the repulsive force of the magnets 28 and 30, the rotating body 21 floats and rotates while being freely movable in the vertical direction. Therefore, the mutual repulsion of the magnets 30°32 and the rotating body 2
When the ratio of the natural vibration determined by the mass of 1 to the rotational speed becomes an integral multiple, a resonance phenomenon occurs, and the vibration tends to become larger and larger.

At this time, by devising the shape of the first gap 24 shown in FIG. 1, it is possible to completely prevent the resonance from becoming larger and larger. That is, a gap sufficient to allow the first gap 24 to absorb resonance energy may be set between the fixed shaft 23 and the rotating body 21.

However, the rotational speed (rpm) of the rotating body was further improved and the first
At the stage when it is no longer possible to fully absorb the resonance energy only by the air gap, fluid existing outside the rotating body 21, such as air, connects the rotating body 21 and the fixed shaft 23 through the through hole 28 shown in FIG. By going in and out of the second gap 26 that is formed, a so-called Dunn ξ effect is produced and vibration energy is absorbed, thereby preventing vibrations of related members due to resonance phenomena.

FIG. 3 shows another embodiment of the present invention. Fluid enters and exits the second gap 26 from the outside through a through hole 30 formed in the fixed shaft 23. Further, FIG. 4 shows the entire configuration in which the ability groups shown in FIGS. 2 and 3 are combined. In other words, the hole 28 drilled in the rotating body 21 and the hole 29 drilled in the fixed shaft 23 are fully valved to allow fluid to enter and exit the second gap 26 from the outside, thereby reducing the vibration of the related parts due to the resonance phenomenon. (
Prevents all vibrations. Of course, the same objective can also be achieved by completely using damping steel for the fixed shaft and rotating body.

(Effects of the Invention) In the present invention, instead of fully employing a magnetically levitated hydrodynamic bearing device with a complicated structure as used in the conventional example, a radial bearing formed by a fixed shaft and a rotating body is used. Effects such as being able to easily absorb vibrations of the bearing member caused by resonance phenomena by fully adjusting the size of the gap in the direction or by drilling a through hole with an extremely simple shape in the rotating body or fixed shaft. has.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an embodiment of a magnetically levitated fluid bearing included in a damper device according to the present invention. FIG. 2 is a cross-sectional view of another embodiment. Figure 3 also shows a cross-sectional view of one of the FJ routes. FIG. 4 is a cross-sectional view of another embodiment. FIG. 5 is a cross-sectional view of a magnetically levitated fluid bearing equipped with a conventional Dan.6 device. 21... Rotating body 22... Lower frame 23.
...Fixed shaft 24...First gap 26...Second
Gap 28... Hole 29... Hole 3
0...Magnet 32...Magnet

Claims (1)

[Claims] 1. In a magnetically levitated hydrodynamic bearing, in order to adjust the fluid pressure in the thrust direction within the bearing, a gap capable of absorbing the thrust pressure is provided between the fixed shaft and the rotating shaft, or A damper device for a magnetic bearing, characterized in that a hole communicating with the outside is formed in a rotating shaft. 2. A damper device for a magnetic bearing according to claim 1, wherein a hole is formed in the fixed shaft to allow fluid to enter and exit from the outside. 3. A damper device for a magnetic bearing according to claim 1, wherein the rotary shaft and the fixed shaft are each provided with holes through which fluid can enter and exit from the outside.